Effect of thickness ratio on mechanical properties and tribological behavior of TiB2/Cr multilayer coatings

Abstract The design of TiB2-based coating with Cr interlayer can offer an efficient way to improve its mechanical properties and tribological performance. The stress distribution of the TiB2/Cr multilayer coatings was optimized by varying the ceramic-metal thickness ratio (Q). As Q decreased from 1.0 to 0.5, the hardness of the deposited TiB2/Cr multilayer coatings drop from 30.3 GPa to 20.2 GPa. However, their fracture toughness and adhesion strength are promoted. The multilayer coating with Q = 0.5 exhibited the best toughness, crack propagation resistance (CPRs), and the smallest equivalent stress area, resulting in the best wear resistance. The wear mechanism of the TiB2 interlayer is primarily abrasive, while that of the Cr interlayer is adhesive. However, reducing Q further to 0.3 led to decreased wear resistance due to low hardness and significant stress concentration. This indicates that there is an optimal balance between hardness, toughness, and stress distribution for achieving improved wear resistance for the multilayer design. Additionally, a notable correlation was found between CPRs and the wear resistance of TiB2/Cr multilayer coatings. CPRs could serve as a reliable predictor for the tribological performance of the ceramic coatings.